Synthesis and Sintering of Ti3SiC2–SiC Composites through Reactive Hot-Pressing of TiC and Si Precursors

MAX phases are an attractive class of layered solids that have recently attracted a great deal of attention due to their unusual and unique composition. The ternary compound Ti3SiC2 is an example of a material that combines the properties of ceramics and metals. As a ceramic, they are high stiff. Some of them are resistant to oxidation, creep, fatigue, corrosion. They are extremely refractory and have a high melting temperature. Also, their strength remains stable with temperature. When considered as a metal, this compound is a conductor of electricity and thermal and is not prone to thermal shock, has easy machining with a variety of modern tools, is relatively soft and also has high chemical resistance. Combining SiC with Ti3SiC2 for fabrication the composite is an effective way to improve the high temperature properties, because SiC as a reinforcing phase has good oxidation resistance, high hardness, abrasion resistance, and in addition, it is compatible with Ti3SiC2 at high temperatures. Fully-dense Ti3SiC2 –SiC composites were in-situ synthesized and sintered through a reactive hot-pressing process using TiC and Si powders with different molar ratios of 3TiC:3Si, 3TiC:2Si (stoichiometric composition), and 3TiC:1.5Si. Phase characterization of the hot-pressed specimens was performed by X-ray diffraction (XRD) analysis, and the microstructures were studied by scanning electron microscope (SEM). The mechanical properties of the hot-pressed composites were investigated in terms of Vickers hardness, fracture toughness, and flexural strength. It was found that the in-situ synthesized SiC particles, with platelet morphology, have been distributed in the in-situ formed Ti3SiC2 matrix. The highest Vickers hardness belonged to the 3TiC:1.5Si sample with a value of 14.2 GPa, related to the presence of SiC and residual TiC phase in the microstructure. The flexural strength enhanced with increasing the molar value of Si, due to the presence of the free Si phase in the sample and the further formation of the SiC phase. The 3TiC:3Si sample achieved the highest fracture toughness of 10.1 MPa.m1/2 and the highest flexural strength of 576 MPa.